When to diversify,and with whom? Choosing partners among out-group strangers in lowland Bolivia

Evidence from the ethnographic and archaeological records reveals that humans often rely on out-group relationships for access to non-local resources and resource buffering. However, little is known about how actors choose out-group cooperative partners. The existing literature suggests that (in-group) partner choice is based on characteristics associated with greater cooperation (e.g., trustworthiness and productivity). Is out-group partner choice based on the same criteria as in-group? Because out-groups may be unique sources of resource access, we suggest that out-group partner choice should track characteristics of both the candidate partner and the partner's group that are associated with benefits for the actor. To assess partner choice, we employed a non-anonymous, one-shot economic game where participants could allocate money towards in-group and out-group strangers. Participants were from three populations of Bolivian horticulturalists (n = 200) that range in their market integration and their mobility, thus capturing variation in potential benefits to out-group cooperation. We find that individual-level qualities of prospective partners, such as wealth and trustworthiness, affect allocation behavior differently for in-group vs out-group prospective partners. While we find no consistent effects of perceived group qualities on a donor's giving to in-group and out-group members, the relevance of out-group market resource access for Tsimane' donors' allocations suggests that, at least when it comes to dividing a limited resource, qualities associated with a group can affect partner preference. Taken together, results provide insight into patterns of intergroup relationship building that have been crucial in the human lineage.     

Oxytocin modulates cooperation within and competition between groups: an integrative review and research agenda

The author reviews evidence that hypothalamic release (or infusion) of the neuropeptide oxytocin modulates the regulation of cooperation and conflict among humans because of three reasons. First, oxytocin enables social categorization of others into in-group versus out-group. Second, oxytocin dampens amygdala activity and enables the development of trust. Third, and finally, oxytocin up-regulates neural circuitries (e.g., inferior frontal gyrus, ventromedial prefrontal cortex, caudate nucleus) involved in empathy and other-concern. Consistent with an evolutionary perspective on the functionality of cooperation, it is concluded that oxytocin-motivated cooperation is mostly parochial-it motivates (i) in-group favoritism, (ii) cooperation towards in-group but not out-group members, and (iii) defense-motivated non-cooperation towards threatening outsiders. Thus, in addition to its well-known role in reproduction and pair-bond formation, oxytocin's primary functions include in-group "tend-and-defend." This review concludes with avenues for new research on oxytocin's functions in within-group cooperation and between-group competition. This article is part of a Special Issue entitled Oxytocin, Vasopressin, and Social Behavior.     

Social exchange and solidarity: in-group love or out-group hate?

Men exhibit a stronger tendency to favor the in-group over the out-group compared to women. We examined whether this male-specific “coalitional psychology” represents in-group love or out-group hate. One hundred thirty-three college freshmen played a prisoner's dilemma game with a member of their own group and a member of another group. Both groups consisted of same-sex participants. An in-group bias (cooperation with the in-group at a level higher than cooperation with the out-group) based on expectations of cooperation from the in-group was observed for both men and women. When such expectations were experimentally eliminated, women did not show any in-group bias, whereas men still exhibited an in-group bias. This male-specific in-group bias was found to be a product of intragroup cooperation (in-group love) rather than a product of intergroup competition (out-group hate). These findings suggest that the male-specific coalitional psychology caters more toward the promotion of within-group solidarity than aggression against the out-group.     

Oxytocin Motivates Non-Cooperation in Intergroup Conflict to Protect Vulnerable In-Group Members

Intergroup conflict is often driven by an individual''s motivation to protect oneself and fellow group members against the threat of out-group aggression, including the tendency to pre-empt out-group threat through a competitive approach. Here we link such defense-motivated competition to oxytocin, a hypothalamic neuropeptide involved in reproduction and social bonding. An intergroup conflict game was developed to disentangle whether oxytocin motivates competitive approach to protect (i) immediate self-interest, (ii) vulnerable in-group members, or (iii) both. Males self-administered oxytocin or placebo (double-blind placebo-controlled) and made decisions with financial consequences to themselves, their fellow in-group members, and a competing out-group. Game payoffs were manipulated between-subjects so that non-cooperation by the out-group had high vs. low impact on personal payoff (personal vulnerability), and high vs. low impact on payoff to fellow in-group members (in-group vulnerability). When personal vulnerability was high, non-cooperation was unaffected by treatment and in-group vulnerability. When personal vulnerability was low, however, in-group vulnerability motivated non-cooperation but only when males received oxytocin. Oxytocin fuels a defense-motivated competitive approach to protect vulnerable group members, even when personal fate is not at stake.     

Oxytocin induces penile erection and yawning when injected into the bed nucleus of the stria terminalis: Involvement of glutamic acid,dopamine, and nitric oxide

Oxytocin (5–100 ng), but not Arg⁸-vasopressin (100 ng), injected unilaterally into the bed nucleus of the stria terminalis (BNST) induces penile erection and yawning in a dose-dependent manner in male rats. The minimal effective dose was 20 ng for penile erection and 5 ng for yawning. Oxytocin responses were abolished not only by the oxytocin receptor antagonist d(CH₂)₅Tyr(Me)²-Orn⁸-vasotocin (1 μg), but also by (+) MK-801 (1 μg), an excitatory amino acid receptor antagonist of the N-methyl-d-aspartic acid (NMDA) subtype, SCH 23390 (1 μg), a D1 receptor antagonist, but not haloperidol (1 μg), a D2 receptor antagonist, and SMTC (40 μg), an inhibitor of neuronal nitric oxide synthase, injected into the BNST 15 min before oxytocin. Oxytocin-induced penile erection, but not yawning, was also abolished by CNQX (1 μg), an excitatory amino acid receptor antagonist of the AMPA subtype. In contrast, oxytocin responses were not reduced by bicuculline (20 ng), a GABA_A receptor antagonist, phaclofen (5 μg), a GABA_B receptor antagonist, CP 376395, a CRF receptor-1 antagonist (5 μg), or astressin 2B, a CRF receptor-2 antagonist (150 ng). Considering the ability of NMDA (100 ng) to induce penile erection and yawning when injected into the BNST and the available evidence showing possible interaction among oxytocin, glutamic acid, and dopamine in the BNST, oxytocin possibly activates glutamatergic neurotransmission in the BNST. This in turn leads to the activation of neural pathways projecting back to the paraventricular nucleus, medial preoptic area, ventral tegmental area, and/or ventral subiculum/amygdala, thereby inducing penile erection and yawning.     

Oxytocin attenuates deficits in social interaction but not recognition memory in a prenatal valproic acid-induced mouse model of autism

Recent studies have reported that oxytocin ameliorates behavioral abnormalities in both animal models and individuals with autism spectrum disorders (ASD). However, the mechanisms underlying the ameliorating effects of oxytocin remain unclear. In this study, we examined the effects of intranasal oxytocin on impairments in social interaction and recognition memory in an ASD mouse model in which animals are prenatally exposed to valproic acid (VPA). We found that a single intranasal administration of oxytocin restored social interaction deficits for up to 2 h in mice prenatally exposed to VPA, but there was no effect on recognition memory impairments. Additionally, administration of oxytocin across 2 weeks improved prenatal VPA-induced social interaction deficits for at least 24 h. In contrast, there were no effects on the time spent sniffing in control mice. Immunohistochemical analysis revealed that intranasal administration of oxytocin increased c-Fos expression in the paraventricular nuclei (PVN), prefrontal cortex, and somatosensory cortex, but not the hippocampal CA1 and CA3 regions of VPA-exposed mice, suggesting the former regions may underlie the effects of oxytocin. These findings suggest that oxytocin attenuates social interaction deficits through the activation of higher cortical areas and the PVN in an ASD mouse model.     

Sub-arachnoid ketamine administration combined with or without misoprostol/oxytocin to facilitate cervical dilation in ewes: A case study

The cervical anatomy limits the use of trans-cervical artificial insemination (AI) and embryo transfer in ewes. Thus, the objective of the study was to evaluate the sub-arachnoid administration of ketamine as a tool to be used in cervical dilation of the ewe. The following experimental treatments were used: in Experiment 1, animals (n = 6) were treated with the sub-arachnoid administration of ketamine (KS, 1.5 mg kg⁻¹); and in Experiment 2, one tablet of misoprostol was diluted in 1.5 ml saline and deposited near the cervical os, 5 h before the trial + oxytocin administered i.v. 5 min before the reproductive procedures (MO, 200 + 20 U.I., respectively). In Experiment 3, animals received sub-arachnoid ketamine + misoprostol/oxytocin (KSMO). The systemic effects, analgesia, sedation, and motor neuron block were evaluated before each experiment and at pre-determined time intervals thereafter. A subjective score system was used to assess pain and discomfort during the reproductive manipulations in the different experiments. The mean duration of analgesia in the sternal decubitus position without sedation was 30 ± 4 and 25 ± 7 min for the KS and KSMO treatments, respectively. All treatments provided sufficient cervical dilation for the passage of the insemination rod into the uterus. The ketamine sub-arachnoid treatment alone produced a complete cervical dilation, allowing easy passage of the rod. Further studies are needed to establish whether this anesthetic technique may interfere with fertility, pregnancy or lambing rate in ewes during AI or embryo transfer.     

Comparison of four techniques to estimate milk production in singleton-rearing non-dairy ewes

Accurate estimates of milk production or milk intake are difficult, as all methods interfere to some degree with the natural behaviour of the dam and her young, and potentially alter milk yield itself. The present study compared milk yield obtained by the “oxytocin” method, udder dimensions (UD), the isotope dilution method, and live weight change of the lamb, in an attempt to select the most accurate and convenient way of measuring milk production in non-dairy sheep. In addition, the study investigated which of the three milk-estimation techniques was an accurate predictor of growth rates of lambs. Thirty-seven singleton-bearing and rearing ewes were milked once a week, for seven consecutive weeks, using the “oxytocin” method. Prior to each afternoon milking, the external dimensions of the ewe's udder were measured. Lambs were weighed weekly for the first seven weeks of life and live weight change was calculated. The deuterium oxide (D₂O) dilution technique was used to estimate milk intake of the lambs and performed at approximately 7 days post-partum and finishing on approximately day 14. Pearson's correlation coefficients and multiple regression coefficients among techniques were calculated. The UD-models at d7 (R² = 0.35), d35 (R² = 0.36) and d42 (R² = 0.34), were the best models explaining variation in milk yield (concordance correlation coefficient (CCC) = 0.49; 0.53; 0.51; for d7, d35 and d42, respectively). The lamb live weight-change model explained the variation in milk yield best at d28 (R² = 0.32; CCC = 0.49), at d35 (R² = 0.22; CCC = 0.36) and at d42 (R² = 0.28; CCC = 0.44). At d14, the intake of milk by lambs as measured by the D₂O technique, did not explain the variation in milk yield. In conclusion, udder dimensions, lamb live weight change and lamb milk intake are relatively poor estimators of the milk yield of singleton-rearing ewes obtained by the “oxytocin” method. Additionally, udder dimensions, milk yield and lamb milk intake do not give an accurate prediction of growth rates of singleton lambs. These results emphasize that there is a difference between ewe milk production potential and lamb milk intake, which need to be considered when estimating milk production in non-dairy animals.     

Neuromuscular control of scapula muscles during a voluntary task in subjects with Subacromial Impingement Syndrome. A case-control study

Imbalance of neuromuscular activity in the scapula stabilizers in subjects with Subacromial Impingement Syndrome (SIS) is described in restricted tasks and specific populations. Our aim was to compare the scapular muscle activity during a voluntary movement task in a general population with and without SIS (n = 16, No-SIS = 15).Surface electromyography was measured from Serratus anterior (SA) and Trapezius during bilateral arm elevation (no-load, 1 kg, 3 kg). Mean relative muscle activity was calculated for SA and the upper (UT) and lower part of trapezius (LWT), in addition to activation ratio and time to activity onset. In spite of a tendency to higher activity among SIS 0.10–0.30 between-group differences were not significant neither in ratio of muscle activation 0.80–0.98 nor time to activity onset 0.53–0.98.The hypothesized between-group differences in neuromuscular activity of Trapezius and Serratus was not confirmed. The tendency to a higher relative muscle activity in SIS could be due to a pain-related increase in co-activation or a decrease in maximal activation. The negative findings may display the variation in the specific muscle activation patterns depending on the criteria used to define the population of impingement patients, as well as the methodological procedure being used, and the shoulder movement investigated.     

Enzymes that control the thiamine diphosphate pool in plant tissues. Properties of thiamine pyrophosphokinase and thiamine-(di)phosphate phosphatase purified from Zea mays seedlings

The pool of thiamine diphosphate (TDP), available for TDP-dependent enzymes involved in the major carbohydrate metabolic pathways, is controlled by two enzyme systems that act in the opposite directions. The thiamine pyrophosphokinase (TPK) activates thiamine into TDP and the numerous phosphatases perform the reverse two-step dephosphorylation of TDP to thiamine monophosphate (TMP) and then to free thiamine. Properties and a possible cooperation of those enzymes in higher plants have not been extensively studied. In this work, we characterize highly purified preparations of TPK and a TDP/TMP phosphatase isolated from 6-day Zea mays seedlings. TPK was the 29-kDa monomeric protein, with the optimal activity at pH 9.0, the K_m values of 12.4 μM and 4.7 mM for thiamine and ATP, respectively, and the V_max value of 360 pmol TDP min^?1 mg^?1 protein. The enzyme required magnesium ions, and the best phosphate donor was GTP. The purified phosphatase was the dimer of 24 kDa subunits, showed the optimal activity at pH 5.0 and had a rather broad substrate specificity, although TDP, but not TMP, was one of the preferable substrates. The K_m values for TDP and TMP were 36 μM and 49 μM, respectively, and the V_max value for TDP was significantly higher than for TMP (164 versus 60 nmoles min^?1 mg^?1 protein). The total activities of TPK and TDP phosphatases were similarly decreased when the seedlings were grown under the illumination, suggesting a coordinated regulation of both enzymes to stabilize the pool of the essential coenzyme.     

Efecto de los movimientos explosivos y de impacto aplicados en piscina sobre la composición corporal,la fuerza y la densidad mineral ósea de mujeres mayores de 60 años

BackgroundOsteoporosis is characterised by loss of bone mass and deterioration of bone tissue microarchitecture that leads to fragility related to the risk of fractures. The aim of the study is to analyse the effects of a training program based on explosive movements and impact, assessed in a swimming pool, on body composition, explosive strength and bone mineral density in women over 60 years old.Material and methodsA total of 35 healthy physically active women (60 ± 4.19 years) were divided into a training pool group using multi jumps (JG) and a control group (CG). JG trained for 24 weeks, 3 times a week, an hour and a half per session. Body composition testing, explosive strength, and bone mineral density were assessed before and after the program.ResultsThere were differences in the explosive force (JG vs CG = P < .05 to .001) and the estimated power (JG vs CG = P < .05 to .002) between JG vs CG, with significant increases in JG. There were no significant differences in the percentage of fat and lean mass, bone mineral density lumbar and femoral between groups, although slightly significant increases in bone mineral density lumbar and femoral could be seen in JG after program implementation (JG pre-test vs JG post- test = P < .05).ConclusionsThe training program with impact and explosive movements assessed in a pool induces gains in muscle strength and power with slight adaptations in body mass index in women over 60 years.     

The harmful alga Aureococcus anophagefferens utilizes 19′-butanoyloxyfucoxanthin as well as xanthophyll cycle carotenoids in acclimating to higher light intensities

Aureococcus anophagefferens is a picoplanktonic microalga that is very well adapted to growth at low nutrient and low light levels, causing devastating blooms (“brown tides”) in estuarine waters. To study the factors involved in long-term acclimation to different light intensities, cells were acclimated for a number of generations to growth under low light (20 μmol photons m^? 2 s^? 1), medium light (60 or 90 μmol photons m^? 2 s^? 1) and high light (200 μmol photons m^? 2 s^? 1), and were analyzed for their contents of xanthophyll cycle carotenoids (the D pool), fucoxanthin and its derivatives (the F pool), Chls c₂ and c₃, and fucoxanthin Chl a/c polypeptides (FCPs). Higher growth light intensities resulted in increased steady state levels of both diadinoxanthin and diatoxanthin. However, it also resulted in the conversion of a significant fraction of fucoxanthin to 19′-butanoyloxyfucoxanthin without a change in the total F pool. The increase in 19′-butanoyloxyfucoxanthin was paralleled by a decrease in the effective antenna size, determined from the slope of the change in F₀ as a function of increasing light intensity. Transfer of acclimated cultures to a higher light intensity showed that the conversion of fucoxanthin to its derivative was a relatively slow process (time-frame of hours). We suggest the replacement of fucoxanthin with the bulkier 19′-butanoyloxyfucoxanthin results in a decrease in the light-harvesting efficiency of the FCP antenna and is part of the long-term acclimative response to growth at higher light intensities.     

Patients with chronic,but not episodic,migraine display altered activity of their neck extensor muscles

The current study aimed to investigate differences in activity of neck flexor and extensor muscles in women with migraine considering the chronicity of their condition. Thirty-one subjects with episodic migraine, 21 with chronic migraine and 31 healthy controls participated. Surface electromyography signals were recorded bilaterally from the sternocleidomastoid, anterior scalene, splenius capitis and upper trapezius muscles as subjects performed 5 stages of cranio-cervical flexion (CCF), representing a progressive increase in range of CCF motion. Comparison of normalized root-mean-square among groups was conducted with 3 × 5 ANCOVA with task level as the within-subject variable, group as the between-subject variable, and the presence of neck pain and disability as co-variates. The group with chronic migraine exhibited increased activity of their extensor muscles compared to the control and episodic migraine groups (splenius capitis: F = 3.149, P = 0.045; upper trapezius: F = 3.369, P = 0.041). No significant between-group differences were found for the superficial neck flexors (sternocleidomastoid: F = 1.161, P = 0.320; anterior scalene: F = 0.135, P = 0.874). In conclusion, women with chronic migraine exhibit increased activity of their superficial neck extensor muscles when acting as antagonists during low-load isometric CCF contractions in comparison to non-headache subjects.     

Intérêt potentiel des images paramétriques des temps d’éjection et de relaxation en tomoscintigraphie des cavités cardiaques dans l’évaluation des cardiopathies asynchrones

Intraleft dyssynchrony is strongly correlated to contractile dysfunction associated to severe heart failure. Dyssynchrony is also a predictive marker for cardiac resynchronization therapy response. We measured dyssynchrony values for both ventricles from gated blood pool SPECT images.Material and methodsThree groups of patients were sampled from normal patients (n = 7), mild heart failure patients (n = 24) and severe heart failure patients (n = 9). Time-derivative parametric images were obtained from 24-time bins gated blood pool SPECT data. We measured intraleft and interventricular contractile and relaxing dyssynchrony values from these images.ResultsIntraleft dispersions values linked to ventricular peak emptying rate were 107 ± 21 ms, 141 ± 58 ms and 515 ± 104 ms for each of the three groups. The values linked to left ventricular peak filling rate were 122 ± 62 ms, 219 ± 117 ms and 603 ± 164 ms respectively. Statistical significant differences (p < 0.01) were observed both for contractile and relaxing phases for severe heart failure patients. Mild heart failure patients had isolated statistical significant (p < 0.01) alterations of the ventricular relaxing phase. Correlation between isotopic dyssynchrony values and left ejection fraction led to a R square coefficient of 0.71 and 0.64 for time to peak emptying and to peak filling respectively. Correlation to QRS width values led to a R square coefficient of 0.76 and 0.62 respectively.ConclusionVentricular dyssynchrony correlated to the importance of the ventricular mechanical dysfunctions is a robust predictor of heart failure. Separate analysis of contractile and relaxing dyssynchrony may lead to a better understanding and characterization of the mechanical dysfunctions involved in heart failure.     

Oxytocin inhibits pentylentetrazol-induced seizures in the rat

We aimed to reveal the anti-convulsant effects of oxytocin (OT) in pentylenetetrazol (PTZ)-induced seizures in rats. Thirty rats were randomly divided into 5 equal groups. Using stereotaxy, we implanted electroencephologram (EEG) electrodes in the left nucleus of the posterior thalamus. After 2 days, the first and second groups were used as the control and PTZ (35 mg/kg) groups, respectively. We administered 40, 80 and 160 nmol/kg OT + 35 mg/kg PTZ to the rats, constituting the third, fourth, and fifth groups, respectively, for 5 days. At the end of 5 days, we recorded EEGs via bipolar EEG electrodes. After 12 h, all groups except the first received 70 mg/kg PTZ and we determined the dose–response ratio. Racine's Convulsion Scale was used to evaluate seizures. The spike–wave complex percentage in the EEG was determined as 0% for the first group, 38.6% ± 7.2 for the second group, 36.4% ± 5.6 for the third group, 4.3% ± 1.8 for the fifth group and 4.1% ± 1.1 for the fifth group. The fourth and fifth groups had significantly decreased spike–wave complex percentages compared to the second group (p < 0.0001). OT may prevent PTZ-induced epilepsy on an EEG. OT may also be considered for use in the treatment of epilepsy in the future.     

Intranasal oxytocin,but not vasopressin,augments neural responses to toddlers in human fathers

This study investigates paternal brain function with the hope of better understanding the neural basis for variation in caregiving involvement among men. The neuropeptides oxytocin (OT) and vasopressin (AVP) are implicated in paternal caregiving in humans and other species. In a double-blind, placebo-controlled, within-subject pharmaco-functional MRI experiment, we randomized 30 fathers of 1–2 year old children to receive either 24 IU intranasal OT before one scan and placebo before the other scan (n = 15) or 20 IU intranasal AVP before one scan and placebo before the other scan (n = 15). Brain function was measured with fMRI as the fathers viewed pictures of their children, unknown children and unknown adults, and as they listened to unknown infant cry stimuli. Intranasal OT, but not AVP, significantly increased the BOLD fMRI response to viewing pictures of own children within the caudate nucleus, a target of midbrain dopamine projections, as well as the dorsal anterior cingulate (dACC) and visual cortex, suggesting that intranasal oxytocin augments activation in brain regions involved in reward, empathy and attention in human fathers. OT effects also varied as a function of order of administration such that when OT was given before placebo, it increased activation within several reward-related structures (substantia nigra, ventral tegmental area, putamen) more than when it was given after placebo. Neither OT nor AVP had significant main effects on the neural response to cries. Our findings suggest that the hormonal changes associated with the transition to fatherhood are likely to facilitate increased approach motivation and empathy for children, and call for future research that evaluates the potential of OT to normalize deficits in paternal motivation, as might be found among men suffering from post-partum depression.     

Developmental change and sexual difference in synaptic modulation produced by oxytocin in rat substantia gelatinosa neurons

We have previously reported that oxytocin produces an inward current at a holding potential of ?70 mV without a change in glutamatergic excitatory transmission in adult male rat spinal lamina II (substantia gelatinosa; SG) neurons that play a pivotal role in regulating nociceptive transmission. Oxytocin also enhanced GABAergic and glycinergic spontaneous inhibitory transmissions in a manner sensitive to a voltage-gated Na⁺-channel blocker tetrodotoxin. These actions were mediated by oxytocin-receptor activation. Such a result was different from that obtained by other investigators in young male rat superficial dorsal horn neurons in which an oxytocin-receptor agonist enhanced glutamatergic and GABAergic but not glycinergic spontaneous transmissions. In order to know a developmental change and also sexual difference in the actions of oxytocin, we examined its effect on spontaneous synaptic transmission in adult female and young male rat SG neurons by using the whole-cell patch-clamp technique in spinal cord slices. In adult female rats, oxytocin produced an inward current at ?70 mV without a change in excitatory transmission. GABAergic and glycinergic transmissions were enhanced by oxytocin, the duration of which enhancement was much shorter than in adult male rats. In young (11–21 postnatal days) male rats, oxytocin produced not only an inward but also outward current at ?70 mV, and presynaptically inhibited or facilitated excitatory transmission, depending on the neurons tested; both GABAergic and glycinergic transmissions were enhanced by oxytocin. The inhibitory transmission enhancements in adult female and young male rats were sensitive to tetrodotoxin. Although the data may not be enough to be estimated, it is suggested that synaptic modulation by oxytocin in SG neurons, i.e., cellular mechanism for its antinociceptive action, exhibits a developmental change and sexual difference.     

Salivary vasopressin increases following intranasal oxytocin administration

Extant research has documented the effects of intranasal administration of oxytocin (OT), and to a lesser degree Arginine Vasopressin (AVP) – two structurally-related neuropeptides – on brain and behaviour, yet the effects of exogenous manipulation of one on circulating levels of the other remain unknown. Studies have shown that OT administration impacts the peripheral levels of numerous hormones; however, whether OT administration also increases AVP concentrations has not been explored. Utilizing a double-blind placebo-controlled within-subject design, ten male and female subjects provided ten saliva samples over four consecutive hours: at baseline and nine times following OT administration. Results indicate that salivary AVP increased in the first hour following OT manipulation (OT condition: mean AVP = 2.17 pg/ml, SE = 28, placebo condition: mean AVP = 1.42 pg/ml, SE = .18) but returned to baseline levels at the next assessment (80 min) and remained low for the remaining period. Similar to OT, AVP showed high degree of individual stability and baseline levels of AVP correlated with AVP concentrations at the first and second post-administration hours regardless of drug condition (Pearson r = .85–.93). Validity of salivary AVP ELISA measurement was verified by demonstrating individual stability of salivary AVP over a six-month period (r = .70, p < .000) as well correlation with plasma levels over the same period (r = .32, p = .037) in a sample of 45 young adults who did not participate in the current study. Overall, findings suggest a potential crosstalk between OT and AVP and indicate that baseline levels of the two neuropeptides may shape the degree to which these systems respond to exogenous manipulation.     

Cooperation and conflict: field experiments in Northern Ireland

The idea that cohesive groups, in which individuals help each other, have a competitive advantage over groups composed of selfish individuals has been widely suggested as an explanation for the evolution of cooperation in humans. Recent theoretical models propose the coevolution of parochial altruism and intergroup conflict, when in-group altruism and out-group hostility contribute to the group''s success in these conflicts. However, the few empirical attempts to test this hypothesis do not use natural groups and conflate measures of in-group and unbiased cooperative behaviour. We conducted field experiments based on naturalistic measures of cooperation (school/charity donations and lost letters'' returns) with two religious groups with an on-going history of conflict—Catholics and Protestants in Northern Ireland. Conflict was associated with reduced donations to out-group schools and the return of out-group letters, but we found no evidence that it influences in-group cooperation. Rather, socio-economic status was the major determinant of cooperative behaviour. Our study presents a challenge to dominant perspectives on the origins of human cooperation, and has implications for initiatives aiming to promote conflict resolution and social cohesion.